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| 2 | <head> | |
| 3 | <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> | |
| 4 | <title>Class protected_fixedsize</title> | |
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| 7 | <link rel="home" href="../../index.html" title="Chapter 1. Context"> | |
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| 24 | </div> | |
| 25 | <div class="section"> | |
| 26 | <div class="titlepage"><div><div><h3 class="title"> | |
| 27 | <a name="context.stack.protected_fixedsize"></a><a class="link" href="protected_fixedsize.html" title="Class protected_fixedsize">Class <span class="emphasis"><em>protected_fixedsize</em></span></a> | |
| 28 | </h3></div></div></div> | |
| 29 | <p> | |
| 30 | <span class="bold"><strong>Boost.Context</strong></span> provides the class <span class="emphasis"><em>protected_fixedsize_stack</em></span> | |
| 31 | which models the <span class="emphasis"><em>stack-allocator concept</em></span>. It appends | |
| 32 | a guard page at the end of each stack to protect against exceeding the stack. | |
| 33 | If the guard page is accessed (read or write operation) a segmentation fault/access | |
| 34 | violation is generated by the operating system. | |
| 35 | </p> | |
| 36 | <div class="important"><table border="0" summary="Important"> | |
| 37 | <tr> | |
| 38 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> | |
| 39 | <th align="left">Important</th> | |
| 40 | </tr> | |
| 41 | <tr><td align="left" valign="top"><p> | |
| 42 | Using <span class="emphasis"><em>protected_fixedsize_stack</em></span> is expensive. That | |
| 43 | is, launching a new coroutine with a new stack is expensive; the allocated | |
| 44 | stack is just as efficient to use as any other stack. | |
| 45 | </p></td></tr> | |
| 46 | </table></div> | |
| 47 | <div class="note"><table border="0" summary="Note"> | |
| 48 | <tr> | |
| 49 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td> | |
| 50 | <th align="left">Note</th> | |
| 51 | </tr> | |
| 52 | <tr><td align="left" valign="top"><p> | |
| 53 | The appended <code class="computeroutput"><span class="identifier">guard</span> <span class="identifier">page</span></code> | |
| 54 | is <span class="bold"><strong>not</strong></span> mapped to physical memory, only | |
| 55 | virtual addresses are used. | |
| 56 | </p></td></tr> | |
| 57 | </table></div> | |
| 58 | <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">context</span><span class="special">/</span><span class="identifier">protected_fixedsize</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> | |
| 59 | ||
| 60 | <span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">traitsT</span> <span class="special">></span> | |
| 61 | <span class="keyword">struct</span> <span class="identifier">basic_protected_fixedsize</span> <span class="special">{</span> | |
| 62 | <span class="keyword">typedef</span> <span class="identifier">traitT</span> <span class="identifier">traits_type</span><span class="special">;</span> | |
| 63 | ||
| 64 | <span class="identifier">basic_protected_fixesize</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span> <span class="special">=</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">default_size</span><span class="special">());</span> | |
| 65 | ||
| 66 | <span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">();</span> | |
| 67 | ||
| 68 | <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&);</span> | |
| 69 | <span class="special">}</span> | |
| 70 | ||
| 71 | <span class="keyword">typedef</span> <span class="identifier">basic_protected_fixedsize</span><span class="special"><</span> <span class="identifier">stack_traits</span> <span class="special">></span> <span class="identifier">protected_fixedsize</span> | |
| 72 | </pre> | |
| 73 | <h5> | |
| 74 | <a name="context.stack.protected_fixedsize.h0"></a> | |
| 75 | <span><a name="context.stack.protected_fixedsize._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"></a></span><a class="link" href="protected_fixedsize.html#context.stack.protected_fixedsize._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"><code class="computeroutput"><span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">()</span></code></a> | |
| 76 | </h5> | |
| 77 | <div class="variablelist"> | |
| 78 | <p class="title"><b></b></p> | |
| 79 | <dl> | |
| 80 | <dt><span class="term">Preconditions:</span></dt> | |
| 81 | <dd><p> | |
| 82 | <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> | |
| 83 | <span class="special"><=</span> <span class="identifier">size</span></code> | |
| 84 | and <code class="computeroutput"><span class="special">!</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> <span class="special">&&</span> | |
| 85 | <span class="special">(</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> <span class="special">>=</span> <span class="identifier">size</span><span class="special">)</span></code>. | |
| 86 | </p></dd> | |
| 87 | <dt><span class="term">Effects:</span></dt> | |
| 88 | <dd><p> | |
| 89 | Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code> | |
| 90 | Bytes and stores a pointer to the stack and its actual size in <code class="computeroutput"><span class="identifier">sctx</span></code>. Depending on the architecture | |
| 91 | (the stack grows downwards/upwards) the stored address is the highest/lowest | |
| 92 | address of the stack. | |
| 93 | </p></dd> | |
| 94 | </dl> | |
| 95 | </div> | |
| 96 | <h5> | |
| 97 | <a name="context.stack.protected_fixedsize.h1"></a> | |
| 98 | <span><a name="context.stack.protected_fixedsize._code__phrase_role__keyword__void__phrase___phrase_role__identifier__deallocate__phrase__phrase_role__special_____phrase___phrase_role__identifier__stack_context__phrase___phrase_role__special___amp___phrase___phrase_role__identifier__sctx__phrase__phrase_role__special_____phrase___code_"></a></span><a class="link" href="protected_fixedsize.html#context.stack.protected_fixedsize._code__phrase_role__keyword__void__phrase___phrase_role__identifier__deallocate__phrase__phrase_role__special_____phrase___phrase_role__identifier__stack_context__phrase___phrase_role__special___amp___phrase___phrase_role__identifier__sctx__phrase__phrase_role__special_____phrase___code_"><code class="computeroutput"><span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> | |
| 99 | <span class="special">&</span> <span class="identifier">sctx</span><span class="special">)</span></code></a> | |
| 100 | </h5> | |
| 101 | <div class="variablelist"> | |
| 102 | <p class="title"><b></b></p> | |
| 103 | <dl> | |
| 104 | <dt><span class="term">Preconditions:</span></dt> | |
| 105 | <dd><p> | |
| 106 | <code class="computeroutput"><span class="identifier">sctx</span><span class="special">.</span><span class="identifier">sp</span></code> is valid, <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> <span class="special"><=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> and <code class="computeroutput"><span class="special">!</span> | |
| 107 | <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> | |
| 108 | <span class="special">&&</span> <span class="special">(</span> | |
| 109 | <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> | |
| 110 | <span class="special">>=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>. | |
| 111 | </p></dd> | |
| 112 | <dt><span class="term">Effects:</span></dt> | |
| 113 | <dd><p> | |
| 114 | Deallocates the stack space. | |
| 115 | </p></dd> | |
| 116 | </dl> | |
| 117 | </div> | |
| 118 | </div> | |
| 119 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
| 120 | <td align="left"></td> | |
| 121 | <td align="right"><div class="copyright-footer">Copyright © 2014 Oliver Kowalke<p> | |
| 122 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
| 123 | file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) | |
| 124 | </p> | |
| 125 | </div></td> | |
| 126 | </tr></table> | |
| 127 | <hr> | |
| 128 | <div class="spirit-nav"> | |
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| 130 | </div> | |
| 131 | </body> | |
| 132 | </html> |